In many machine installations, especially in installations wherein massive portions of the machines are fabricated and machined separately such as in the case of hydraulic turbines, the stay ring is machined, drilled and tapped at one setup. At a later time the outer headcover is machined, spot faced and drilled to provide access openings for the insertion of bolts for joining the outer headcover to the stay ring. In these instances, heavy hex screws with spherical washers are utilized to secure the various members together. It is especially difficult to establish a seal to prevent water leakage around the screws entering into the intermediate headcover cavity. In the past, various types of sealants have been used with varying degrees of success, but none have been completely successful in providing a complete seal to prevent water leakage around the screws and water would fill up the cavity in the headcover and enter into the powerhouse chamber. Lead washers or similar deformable metallic material has been used below the bolt head but this has not proven successful since the lead washers flatten out on one side and split. Rubber has been tried but proven unsuccessful as it did not seal properly and would blow out through the opening.